The potential for large language models (LLMs) to hide messages within plain
text (steganography) poses a challenge to detection and thwarting of unaligned
AI agents, and undermines faithfulness of LLMs reasoning. We explore the
steganographic capabilities of LLMs fine-tuned via reinforcement learning (RL)
to: (1) develop covert encoding schemes, (2) engage in steganography when
prompted, and (3) utilize steganography in realistic scenarios where hidden
reasoning is likely, but not prompted. In these scenarios, we detect the
intention of LLMs to hide their reasoning as well as their steganography
performance. Our findings in the fine-tuning experiments as well as in
behavioral non fine-tuning evaluations reveal that while current models exhibit
rudimentary steganographic abilities in terms of security and capacity,
explicit algorithmic guidance markedly enhances their capacity for information
concealment.